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Even long-term investors try to sell their bitcoins at some point in order to buy even more bitcoins in the subsequent bear market. But there is a big difference in how and when to do it, if it is done without proper knowledge, then it will lead to losses. You can just buy and wait, without any attempts to sell and buy more, in this case there will also be a profit, and for someone this choice will be the best solution if in trading he is not very good.
And for every investment, I believe we must take profits, we need to enjoy profits, that's one of many purposes of investment, even in non-bitcoin or cryptocurrency investment related.
Some also considering having fund for their trading and some are have portfolio for long term where it is separated from their trading account, you can also do this but make sure to take it serious.